Semiconductor device and method of manufacturing the same

ABSTRACT

Even when a stiffener is omitted, the semiconductor device which can prevent the generation of twist and distortion of a wiring substrate is obtained. 
     As for a semiconductor device which has a wiring substrate, a semiconductor chip by which the flip chip bond was made to the wiring substrate, and a heat spreader adhered to the back surface of the semiconductor chip, and which omitted the stiffener for reinforcing a wiring substrate and maintaining the surface smoothness of a heat spreader, a wiring substrate has a plurality of insulating substrates in which a through hole whose diameter differs, respectively was formed, and each insulating substrate contains a glass cloth.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patentapplications No. 2005-121063 filed on Apr. 19, 2005, and No. 2006-096999filed on Mar. 31, 2006, the content of which is hereby incorporated byreference into this application.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device which makes flipchip connection of a semiconductor chip on a wiring substrate, and formsa heat spreader on a back surface of this semiconductor chip, and itsmanufacturing method.

DESCRIPTION OF THE BACKGROUND ART

A semiconductor device which makes flip chip connection of thesemiconductor chip via the bump on the wiring substrate is proposed. Thegap of the semiconductor chip and the wiring substrate is filled up withunder-filling resin in this semiconductor device. In order to make heatradiation property high, a heat spreader is formed on the back surfaceof the semiconductor chip. In order to reinforce a wiring substrate andto maintain the surface smoothness of a heat spreader conventionally, astiffener (reinforcing plate) was formed (for example, refer to PatentReference 1).

What formed the build-up substrate by soft resin coating or a soft filmbeing conventionally stuck on both sides of the hard core substratecontaining a glass cloth was used as a wiring substrate. And wirings offine pitch were formed in the build-up substrate. However, since thebuild-up substrate was soft, the rigidity of the wiring substrate itselfwas not high.

[Patent Reference 1] Japanese Unexamined Patent Publication No.2003-51568

SUMMARY OF THE INVENTION

Since a conventional wiring substrate does not have high rigidity asmentioned above, when the stiffener is omitted for cost reduction, andthe shape is made to have a clearance between the portion which projectsto the perimeter of the chip of the heat spreader, and the wiringsubstrate upper surface, the wiring substrate of the portion whichprojects to the perimeter of the chip becomes the shape where, althougha very portion is covered by under-filling resin, the most exposes, andtwist and distortion of the wiring substrate generate. Hereby, therewere problems that the solder ball joined to the under surface of thewiring substrate floated, or a stress was applied to the edge of thesemiconductor chip.

There was a problem that the adhesion of a semiconductor chip, a wiringsubstrate, and under-filling may not be good, and the gap of thesemiconductor chip and the wiring substrate was not fully filled up withunder-filling resin. And in an argon spatter, argon etc. could not fullybe supplied to the narrow gap of the semiconductor chip and the wiringsubstrate, and the adhesion of the gap concerned has not fully beenimproved.

When the stiffener is omitted for cost reduction, the shape is made tohave a clearance between the portion which projects to the perimeter ofthe chip of the heat spreader, and the wiring substrate upper surface,and heat radiation resin is thin, a crack and a damage will enter intothe semiconductor chip easily. On the other hand, when heat radiationresin is thick, the divergence characteristics of heat will worsen.Therefore, it is necessary to control the thickness of heat radiationresin with high precision.

In the case that the stiffener is omitted, and the shape is made to havea clearance between the portion which projects to the perimeter of thechip of the heat spreader, and the wiring substrate upper surface, whena solder ball is formed on the under surface of the wiring substrate,and doing an electric test of the wiring substrate and the semiconductorchip after that, there was also a problem of the heat spreader havinghit a formation instrument and a test instrument, and damaging.

The present invention was made in order to solve the above problems. Thefirst purpose is to obtain a semiconductor device which can prevent thegeneration of twist and distortion of a wiring substrate, even when thestiffener is omitted.

The second purpose is to obtain a manufacturing method of asemiconductor device which can improve the filling factor of theunder-filling resin in the gap of a semiconductor chip and a wiringsubstrate.

The third purpose is to obtain a semiconductor device which can controlthe thickness of heat radiation resin with high precision, when theshape is made to omit the stiffener and to have a clearance between theportion which projects to the perimeter of the chip of the heatspreader, and the wiring substrate upper surface.

The fourth purpose is to obtain a manufacturing method of asemiconductor device which can prevent a heat spreader's hitting aformation instrument and a test instrument, and damaging in the case offormation of a solder ball, or an electric test, even when the shape ismade to omit the stiffener and to have a clearance between the portionwhich projects to the perimeter of the chip of the heat spreader, andthe wiring substrate upper surface.

The semiconductor device according to a first aspect of the presentinvention comprises: a wiring substrate; a semiconductor chip which isflip-chip-bonded over the wiring substrate; and a heat spreader adheredover a back surface of the semiconductor chip; wherein a stiffener forreinforcing the wiring substrate and maintaining a surface smoothness ofthe heat spreader is omitted; and the wiring substrate has a pluralityof insulating substrates in which a through hole whose diameter differs,respectively is formed, and each insulating substrate contains a glasscloth.

The semiconductor device according to a second aspect of the presentinvention comprises: a wiring substrate; a semiconductor chip which isflip-chip-bonded over the wiring substrate; and a heat spreader adheredover a back surface of the semiconductor chip; wherein a stiffener forreinforcing the wiring substrate and maintaining a surface smoothness ofthe heat spreader is omitted; and the wiring substrate has a pluralityof layers of insulating substrates in which a through hole whosediameter is less than 100 μm is formed, and a plurality of layers ofwiring layers, and the insulating substrate contains a glass cloth.

The method of manufacturing a semiconductor device according to a thirdaspect of the present invention comprises the steps of:flip-chip-bonding a semiconductor chip via a bump over a wiringsubstrate; supplying O₂ plasma in a gap of the wiring substrate and thesemiconductor chip after the step of flip-chip-bonding; and pouringunder-filling resin in the gap of the wiring substrate and thesemiconductor chip after the step of supplying O₂ plasma.

The semiconductor device according to a fourth aspect of the presentinvention comprises: a wiring substrate; a semiconductor chipflip-chip-bonded over the wiring substrate; and a heat spreader adheredover a back surface of the semiconductor chip with heat radiation resin;wherein the heat radiation resin contains a filler; and by setting athickness of the heat radiation resin to A, and a maximum grain size ofthe filler to B_(MAX), a relation: A×⅘ ≦B_(MAX) is held.

The semiconductor device according to a fifth aspect of the presentinvention comprises: a wiring substrate; a semiconductor chipflip-chip-bonded over the wiring substrate; and a heat spreader adheredover a back surface of the semiconductor chip with heat radiation resin;wherein the heat radiation resin contains a filler and a spacer; and bysetting a thickness of the heat radiation resin to A, and an averageparticle diameter of the spacer to C, a relation of A× 9/10 ≦C is held.

The method of manufacturing a semiconductor device according to a sixthaspect of the present invention comprises the steps of:flip-chip-bonding a semiconductor chip over an upper surface of a wiringsubstrate; adhering a heat spreader smaller than the wiring substrateover a back surface of the semiconductor chip; holding the wiringsubstrate by a hold means which touches a portion which is an uppersurface of the wiring substrate and an outside of the heat spreader,turning the upper surface of the wiring substrate down; and joining asolder bump to an under surface of the wiring substrate where the wiringsubstrate is held. The other features of the present invention are madeclear to below.

By the semiconductor device according to the first or second aspect ofthe present invention, even when the shape is made to have a clearancebetween the portion which projects to the perimeter of the chip of theheat spreader, and the wiring substrate upper surface, the generation oftwist and distortion of the wiring substrate can be prevented.

By the method of manufacturing a semiconductor device according to thethird aspect of the present invention, the filling factor of theunder-filling resin in the gap of a semiconductor chip and a wiringsubstrate can be improved.

By the semiconductor device according to the fourth or fifth aspect ofthe present invention, even when the shape is made to have a clearancebetween the portion which projects to the perimeter of the chip of theheat spreader, and the wiring substrate upper surface, the thickness ofheat radiation resin can be controlled with high precision.

By the method of manufacturing a semiconductor device according to thesixth aspect of the present invention, even when the shape is made tohave a clearance between the portion which projects to the perimeter ofthe chip of the heat spreader, and the wiring substrate upper surface, aheat spreader's hitting a formation instrument and a test instrument,and damaging can be prevented in the case of formation of a solder ball.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the wiring substrate of thesemiconductor device concerning Embodiment 1 of the present invention;

FIG. 2 is a top view showing the wiring substrate of the semiconductordevice concerning Embodiment 1 of the present invention;

FIG. 3 is a bottom view showing the wiring substrate of thesemiconductor device concerning Embodiment 1 of the present invention;

FIG. 4 is a side view of a semiconductor chip;

FIG. 5 is a bottom view of a semiconductor chip;

FIG. 6 is a sectional view showing the state where the semiconductorchip was located above wiring substrate 10;

FIG. 7 is a sectional view showing the state that the bump of asemiconductor chip and the bump of a wiring substrate are made to weldby pressure;

FIG. 8 is a top view showing the state where the flip chip bond of thesemiconductor chip was made to the upper surface of the wiringsubstrate;

FIG. 9 is a sectional view showing the state that a wiring substrate anda semiconductor chip are exposed to O₂ plasma;

FIG. 10 is a sectional view showing the state that under-filling resinis poured into the gap of a semiconductor chip and a wiring substrate;

FIG. 11 is a sectional view showing the state that a wiring substrateand a semiconductor chip are put in a baking furnace, and baking isperformed;

FIG. 12 is a sectional view showing the state that heat radiation resinis applied to the back surface of a semiconductor chip;

FIG. 13 is a sectional view showing the state that a heat spreader isadhered on the back surface of a semiconductor chip;

FIG. 14 is a sectional view showing the state that a wiring substrate, asemiconductor chip, and a heat spreader are put in a baking furnace, andbaking is performed;

FIG. 15 is a top view showing the state where the heat spreader wasmounted on the back surface of the semiconductor chip;

FIG. 16 is a sectional view showing the state that the flux is appliedto the under surface of a wiring substrate;

FIG. 17 is a sectional view showing the state where the solder ball waslocated above the wiring substrate;

FIG. 18 is a sectional view showing the state that the wiring substratewhich carried solder ball 37 is put in a reflow furnace, and reflow isperformed;

FIG. 19 is the bottom view of a wiring substrate on which the solderballs were adhered;

FIG. 20 is a sectional view showing the state where alignment of thesolder ball was made on the test pin;

FIG. 21 is a sectional view showing the semiconductor device concerningEmbodiment 1 of the present invention;

FIG. 22 is a sectional view showing the semiconductor device concerningEmbodiment 2 of the present invention; and.

FIG. 23 is a partially expanded cross-sectional view of a semiconductorchip.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

Hereafter, the manufacturing method of the semiconductor deviceconcerning Embodiment 1 of the present invention is explained usingdrawings.

FIG. 1 is a sectional view showing the wiring substrate of thesemiconductor device concerning Embodiment 1 of the present invention,FIG. 2 is the top view, and FIG. 3 is the bottom view.

This wiring substrate 10 puts build-up substrates 12 a and 12 b on theupper surface of core substrate 11, puts build-up substrates 12 c and 12d on the under surface, and is made to unify by thermo-compression usinga vacuum press etc. However, in order to prevent a warp of wiringsubstrate 10, the build-up substrate of the same number of sheets isbonded together to the upper and lower sides of core substrate 11.

And core substrate 11 and build-up substrates 12 a-12 d include a layerin which the glass cloth was impregnated with insulating resin tosolidify into a plate, respectively. Here, the textile fabrics whichinclude long glass textiles, or the nonwoven fabric which includes shortglass textiles is also good as a glass cloth. And the cross whichincludes another insulating materials with high rigidity compared withinsulating resin, for example, a carbon fiber etc., instead of a glasscloth can also be used.

As insulating resin, for example polysulfone, polyether sulfone,polyphenyl sulfone, polyphthalamide, polyamidoimide, polyketone,polyacetal, polyimide, polycarbonate, modified polyphenylene ether,polybutylene terephthalate, polyarylate, polysulfone, polyphenylenesulfide, polyetheretherketone, tetrafluoroethylene, epoxy, bismaleimidesystem resin, etc. can be used.

Through hole 13 is formed in core substrate 11 by the drill. Thediameter of through hole 13 is 100-300 μm, and is 200 μm here. Andthrough hole via 14 which includes Cu etc. is formed at the side wall ofthrough hole 13 by plating etc. Wiring layer 15 which includes Cu etc.is formed on the upper surface of core substrate 11 by an electroplatingmethod, photo lithography, etc. And wiring layer 16 which includes Cuetc. is similarly formed on the under surface of core substrate 11. Thiswiring layer 15 and wiring layer 16 are connected via through hole via14.

Through hole 17 is formed also in build-up substrates 12 a-12 d,respectively. However, since build-up substrates 12 a-12 d are thincompared with core substrate 11, and fine processing is easy for them, adiameter of through hole 17 of build-up substrates 12 a-12 d is smallcompared with that of through hole 13 of core substrate 1, is 30-100 μmconcretely, and is 50 μm here. UV-YAG laser, carbon dioxide gas laser,excimer laser, a dry etching method using plasma, etc. can be used forformation of this through hole 17.

On build-up substrate 12 a-12 d, wiring layer 18 which includes Cu etc.,is respectively formed by an electroplating method, photo lithography,etc. And through hole via 19 is formed in through hole 17 by filling upwith electric conduction paste, such as Cu.

The front surface of wiring substrate 10 is covered by solder resist 20.Opening is formed in this solder resist 20, and a part of top and lowestwiring layer 18 is exposed. As solder resist 20, a resin which iselectrically and thermally excellent, such as an epoxy system, apolyimide system, an acrylic system, and BT system, can be used.

And bump 21 a which includes lead free solder is formed by plating orvacuum deposition on the exposed top wiring layer 18. These bumps 21 aare arranged on wiring substrate 10 in a lattice manner. In FIG. 2,although bumps 21 a are arranged at full matrix form in the region onwhich semiconductor chip 22 is arranged, various arrangement can bechosen suitably. Lead free solder is solder in which lead is notincluded or only lead of the grade (less than 1 wt %) with fewenvironmental impacts is included. Here, what contained Cu 1 to 3% in Snis used as lead free solder.

FIG. 4 is a side view of a semiconductor chip, and FIG. 5 is the bottomview. Bumps 21 b which include lead free solder are formed on themounting surface of semiconductor chip 22 by plating or vacuumdeposition. The partially expanded cross-sectional view of semiconductorchip 22 is described in FIG. 23. Semiconductor chip 22 is provided withsilicon substrate 100, semiconductor element 101 formed on siliconsubstrate 100, such as MOSFET, an interlayer insulation film whichincludes a laminated structure of SiO₂ insulating film 102, SiCN etchingstopper film 103, SiOC low dielectric constant film 104, and SiOFtightly adhering film 105, wiring layer 106 in a chip which includes atungsten plug embedded in this interlayer insulation film, Cu wiring,etc., aluminum pad layer 107 formed on the interlayer insulation film, alaminated film of inorganic passivation film 108 which includes aSiO₂/SiN laminated film, and organic passivation film 109 which includesa polyimide film (PiQ film) in which an opening was formed so thataluminum pad 107 might be exposed, barrier metal 110 which was formed onaluminum pad 107 and which includes, for example a Ti/Cu/Ni laminatedfilm, and solder bump 21 b formed on barrier metal 110. When using afilm of a dielectric constant lower than the dielectric-constant of SiO₂film K=4.3 as an interlayer insulation film in semiconductor chip 22,the strength reduction of the interlayer insulation film poses aproblem. The problem is remarkable in a porous Low-k film which reducesa dielectric constant by reducing the density of a film especially ascompared with the TEOS film which is SiO₂ common film. The technology ofreducing the stress applied to a chip becomes very important, whenimproving the reliability of a semiconductor device. In this embodiment,a porous SiOC film is adopted as a low dielectric constant film. Thisporous SiOC film is methyl-containing polysiloxane which mainly includesmany Si—CH₃ groups, since a gap is generated in molecular structure byexistence of CH₃, it becomes porosity, and the dielectric constant isfalling. As a material which forms semiconductor chip 22, although theexample was shown above, it is not restricted to these. For example, asa low dielectric constant film, a porous low dielectric constant film ofSiOCH base, porous silica system materials, such as a Nano ClusteringSilica film, H-containing polysiloxane which is called porous HSQ,organic polymer film, and a porous film of organic polymer etc. areavailable suitably.

Next, the step which performs flip chip bond of the semiconductor chip22 on the above-mentioned wiring substrate 10 is explained.

First, as shown in FIG. 6, wiring substrate 10 is laid in thepredetermined location on bonding stage 24. And the surface on whichbumps 21 b were formed is turned down, and vacuum adsorption of thesemiconductor chip 22 is made on the under surface of bonding head 25.And horizontal displacement of the bonding head 25 is made, andsemiconductor chip 22 is located above wiring substrate 10.

On this occasion, bonding stage 24 heats wiring substrate 10 to about150° C. with the built-in heater (un-illustrating). Similarly, bondinghead 25 heats semiconductor chip 22 to about 150° C. with the built-inheater (un-illustrating).

Next, bonding head 25 is descended and bump 21 b of semiconductor chip22 and bump 21 a of wiring substrate 10 are made to weld by pressure, asshown in FIG. 7. In this condition, semiconductor chip 22 is heated toabout 260° C. which is more than a solder melting point by bonding head25, and bonding head 25 is made to move (scrub) rhythmicallyperiodically to a horizontal direction or a perpendicular direction,where bumps 21 a and 21 b are melted. As a result, bump 21 a and bump 21b unify, and bump 21 is formed.

Then, bonding head 25 is cooled to temperature lower than a soldermelting point, and bump 21 is solidified. And adsorption ofsemiconductor chip 22 by bonding head 25 is canceled, bonding head 25 israised, and bonding is terminated. FIG. 8 is a top view showing thecondition of having made the flip chip bond of the semiconductor chip tothe upper surface of the wiring substrate.

Since the flip chip bond can be performed for semiconductor chip 22 towiring substrate 10 via bump 21 according to the above-mentioned step,without using flux, the washing process of the flux can be skipped.Since void is not formed in bump 21 by expansion of a flux residue,reliability can be improved.

Next, the step which forms under-filling resin between semiconductorchip 22 and wiring substrate 10 in order to prevent that bump 21 isinjured with thermal stress etc. is explained.

First, as shown in FIG. 9, wiring substrate 10 and semiconductor chip 22are exposed to O₂ plasma. Since this 0 ₂ plasma also enters a slitcompared with an argon spatter etc., O₂ plasma can be supplied also tothe gap of semiconductor chip 22 and wiring substrate 10.

The passivation films (for example, organic resin films, such as apolyimide film) of wiring substrate 10 and semiconductor chip 22 arecleaned and activated (roughened) by this plasma treatment. Hereby,adhesion with the under-filling resin formed later can be improved. Thefilling factor of under-filling resin in the gap of semiconductor chip22 and wiring substrate 10 can be improved.

Next, as shown in FIG. 10, under-filling resin 28 of paste state orliquid state is poured into the gap of semiconductor chip 22 and wiringsubstrate 10. Thermosetting resin, such as an epoxy resin, can be usedas under-filling resin 28, and a filler etc. may be contained.

Here, the under-filling resin whose glass transition temperature (Tg) is100-120° C., for example, 110° C., is used. However, although there arevarious measuring methods of Tg, the DMA method (pull method) is usedhere.

Next, as shown in FIG. 11, wiring substrate 10 and semiconductor chip 22are put in baking furnace 29, and baking of about 6 hours is performedat about 125° C. which is low temperature from the former. This curesunder-filling resin 28.

Thus, the modulus of elasticity of under-filling resin is securable bymaking Tg to more than or equal to 100° C. also at about 125° C.-150° C.which are generally asked for operational reliability. For this reason,a bump can fully be protected.

Resin curing temperature (curing temperature) can be made low by makingTg less than or equal to 120° C. For this reason, after curingunder-filling resin, the difference of temperature at the time of makingit change from resin curing temperature to low temperature can be madesmall, and the internal stress applied to a chip can be made small.

Next, the step which adheres a heat spreader on the back surface (thesurface of the opposite side to the mounting surface) of semiconductorchip 22 is explained.

First, as shown in FIG. 12, heat radiation resin 31 is applied to theback surface of semiconductor chip 22. Next, as shown in FIG. 13, heatspreader 32 is adhered on the back surface of semiconductor chip 22 withheat radiation resin 31. As material of heat spreader 32, Cu, Al,Al—Si—Cu alloy, etc. can be used in consideration of heat radiationproperty.

Since the stiffener is omitted for cost reduction, and the shape is madeto have a clearance more than or equivalent to the thickness of the chipbetween the portion which projects to the perimeter of the chip of theheat spreader, and the wiring substrate upper surface, when heatradiation resin 31 is thin, a crack and a damage will enter intosemiconductor chip 22 easily. On the other hand, when heat radiationresin 31 is thick, the divergence characteristics of heat will worsen.Therefore, it is necessary to control the thickness (gap) of heatradiation resin 31 with high precision.

Then, the size of the filler mixed in heat radiation resin 31 isoptimized, and the thickness of heat radiation resin 31 is controlled.Here, the thing the average particle diameter of whose filler is 13 μmis used. However, since the size of a filler has a distribution, thething whose particle diameter is more than or equal to 45 μm is cutusing a mesh. Hereby, the thickness of heat radiation resin iscontrollable to 60±20 μm.

Namely, by setting the desired thickness of heat radiation resin to A,and the maximum grain size of a filler to B_(MAX), a filler is chosen sothat it may have the relation:A×⅘≧B _(MAX.)Hereby, the thickness of heat radiation resin is controllable withinfixed limits centered on desired thickness. As heat radiation resin 31,it is preferred to use the heat-curing type heat radiation resin of asilicone system from the ease of workability and the height of the heatconductivity. Silicone system heat radiation resin is the resin whichblended highly thermally conductive powders, such as alumina, with thebase of silicone oil. Since it is a product of high viscosity greasestate in the state before cure, the thickness of heat radiation resin 31can be controlled comparatively easily and in quite high accuracy byusing the position control of a jig. As viscosity of heat radiationresin 31, material higher than the viscosity at the time of injection ofunder-filling resin 28 is preferred at least. As maximum grain sizeB_(MAX) of a filler, although not restricted to ⅘ or less of thickness Aof heat radiation resin, it is preferred to have the relation thatmaximum grain size B_(MAX) of a filler is smaller than the portionA_(MIN) at which the thickness becomes the smallest of heat radiationresin. When B_(MAX) becomes the same as A_(MIN), or larger than that,possibility that a filler will be put between heat spreader 32 andsemiconductor chip 22 back surface will become high. Especially when itdoes not have the structure which supports heat spreaders 32, such as astiffener, firmly around semiconductor chip 22 like this embodiment, inthe step which sticks a heat spreader, when it is going to control thethickness of heat radiation resin only by load control, by the fillerinserted between heat spreader 32 and semiconductor chip 22, a crack mayenter into semiconductor chip 22 back surface, and the reliability ofthe semiconductor device may be dropped.

Shape of a filler is made into a globular form and the damage tosemiconductor chip 22 or heat spreader 32 is made small. Here, when theshape of a filler is not a globular form strictly, let the particlediameter of a filler be a diameter of the longest place.

Next, as shown in FIG. 14, wiring substrate 10, semiconductor chip 22,and heat spreader 32 are put in baking furnace 29, baking is performed,and heat radiation resin 31 is cured. This mounts heat spreader 32 onsemiconductor chip 22.

FIG. 15 is a top view showing the state of having mounted heat spreader32 on semiconductor chip 22. Heat spreader 32 is made small comparedwith wiring substrate 10. Hereby, cost can be reduced. However, in orderto secure heat radiation property, heat spreader 32 is made larger thansemiconductor chip 22.

Next, the step which joins the solder ball used as an externalconnection terminal to the under surface of wiring substrate 10 isexplained.

First, as shown in FIG. 16, the upper surface of wiring substrate 10 isturned down, and wiring substrate 10 is held by hold means 33 whichtouches the portion which is the upper surface (surface on whichsemiconductor chip 22 was mounted) of wiring substrate 10 and theoutside of heat spreader 32, and the side surface of wiring substrate10. Hereby, wiring substrate 10 can be held, without giving stress tosemiconductor chip 22 and heat spreader 32.

And where wiring substrate 10 is held, flux 35 is applied to the undersurface of wiring substrate 10 via mask 34. Hereby, flux 35 is appliedto wiring layer 18 exposed on the under surface of wiring substrate 10.However, soldering paste may be applied instead of flux 35.

Next, as shown in FIG. 17, vacuum adsorption of the solder ball 37 whichincludes lead free solder is made to the under surface of ball mountinghead 36. And horizontal displacement of the ball mounting head 36 ismade, and solder ball 37 is located above wiring substrate 10. And ballmounting head 36 is descended and solder ball 37 is mounted on flux 35of wiring substrate 10. Then, adsorption of solder ball 37 by ballmounting head 36 is canceled, and ball mounting head 36 is raised.

Next, as shown in FIG. 18, where wiring substrate 10 is held by holdmeans 33 turning solder ball 37 upwards, putting on conveyor 38, puttingin reflow furnace 39, reflow is performed, and solder ball 37 is joinedto wiring substrate 10. Then, flux 35 is removed by washing. FIG. 19 isa bottom view of the wiring substrate which joined the solder ball.

Next, as shown in FIG. 20, the surface which joined solder ball 37 ofwiring substrate 10 is turned downward, and alignment of the solder ball37 is made on test pin 41 which includes elastic members, such as aspring. And solder ball 37 of wiring substrate 10 is pushed against testpin 41 by pressing down wiring substrate 10 by pressing tool 42 from anupside. However, pressing tool 42 has the space which includes heatspreader 32 and semiconductor chip 22, and presses down the portionwhich is the upper surface of wiring substrate 10 and the outside ofheat spreader 32.

The electric test of wiring substrate 10 and semiconductor chip 22 isdone by exchanging an electrical signal between test pin 41 and solderball 37 in this state.

According to the above steps, the semiconductor device concerningEmbodiment 1 of the present invention as shown in FIG. 21 is completed.Then, the above-mentioned semiconductor device is mounted on a motherboard etc. using solder balls 37.

This semiconductor device omits the stiffener conventionally formed inorder to reinforce the wiring substrate and to maintain the surfacesmoothness of the heat spreader for cost reduction, and has the shapewhich has a clearance more than or equivalent to the thickness of thechip between most portions which project to the perimeter of the chip ofthe heat spreader, and the wiring substrate upper surface. When there ismuch amount of under-filling resin 28, it may become the shape whichfills between the very portion which projects to the perimeter of thechip of the heat spreader and the wiring substrate upper surface, but ascompared with the case where it has a stiffener, the effect ofreinforcement of a wiring substrate is very restrictive. Thus, in theshape which the great portion of wiring substrate upper surface of theperimeter of the chip exposes, the rigidity improvement in the wiringsubstrate itself becomes important. And in wiring substrate 10, a glasscloth is contained not only core substrate 11 but build-up substrate 12a-12 d.

That is, wiring substrate 10 has a plurality of insulating substrates(core substrate 11 and build-up substrates 12 a-12 d) in which a throughhole whose diameter differs, respectively was formed, and eachinsulating substrate contains a glass cloth. Wiring substrate 10 has theinsulating substrate (build-up substrates 12 a-12 d) in which a throughhole whose diameter is 100 μm or less was formed, and this insulatingsubstrate also contains a glass cloth.

Hereby, rigidity can be made high as the wiring substrate 10 whole.Therefore, even when a stiffener is omitted for cost reduction, a warpand a distortion of wiring substrate 10 can be prevented. As comparedwith core substrate 11, formation of a finer through hole is required tothe insulating layer which forms build-up substrates 12 a-12 d. Bymaking the diameter of a through hole small, the area of the portionwhich can arrange a wiring becomes wide and the degree of freedom of awiring layout improves. In particular, when there are many electrodesformed on semiconductor chip 22 as hundreds of or more pieces, i.e., thenumber of bumps 21, securing the layout degree of freedom of wiringlayer 18 of the top layer which connects with bump 21 becomes important.So, securing the forming accuracy in a micro fabrication becomesindispensable at build-up substrate 12 b with which through hole via 19connected to wiring layer 18 of the top layer is formed in the inside.In this embodiment, in order to secure the forming accuracy of build-upsubstrates 12 a-12 d, the thickness of the glass cloth which build-upsubstrate 12 a-12 d contains is made thinner than the thickness of theglass cloth which core substrate 11 contains. The thickness of build-upsubstrates 12 a-12 d is also made thinner than core substrate 11. Thus,by using a thin glass cloth as compared with that of core substrate 11,and making thin build-up substrate 12 a-12 d each layer, formingaccuracy is improved maintaining the rigidity of build-up substrates 12a-12 d, and formation of fine through hole 17 is made easy. When using,for example what has a vulnerable porous low dielectric constant filmetc. as compared with a TEOS film instead of conventional SiO₂interlayer insulation film as semiconductor chip 22 like a descriptionin this embodiment, to adopt build-up substrates 12 a-12 d whichincreased strength by the glass cloth is especially effective. That is,by increasing the strength of build-up substrates 12 a-12 d, theinternal stress exerted on semiconductor chip 22 can be reduced, and thegeneration of peeling in the vulnerable layer of semiconductor chip 22inside can be prevented. It is preferred as semiconductor chip 22 thatorganic system passivation films, such as a polyimide passivation film,are formed on the main surface. Organic system passivation films, suchas polyimide, have high adhesion with under-filling resin 28 as comparedwith inorganic system passivation films, such as a SiN film. By coveringmain surface upper part of semiconductor chip 22 by an organic systempassivation film, peeling at the interface of under-filling resin 28 andsemiconductor chip 22 can be prevented. By maintaining the almost equaladhesion state of the interface of under-filling resin 28 andsemiconductor chip 22, the generation of problems, such as peelinginside the low dielectric constant film by a local stress concentration,can be prevented. In this embodiment, the case where what has highrigidity by containing a glass cloth in each layer was used wasdescribed as wiring substrate 10. However, as a means which improves therigidity of each layer of a wiring substrate, not only limited to themethod of using the glass cloth which wove the glass fiber in the shapeof a cloth, but also the method of using the nonwoven fabric type glasscloth formed by the glass fiber, the method of making the short glassfiber be contained as a reinforcement agent, etc. can be chosensuitably. Also as material of the fiber, not only the glass that usessilica as a base but the material which uses a carbon fiber can bechosen suitably.

Embodiment 2

FIG. 22 is a sectional view showing the semiconductor device concerningEmbodiment 2 of the present invention. The difference with Embodiment 1is using the thing which made thin insulating substrates 43 a-43 d inwhich the through hole less than or equal to 100 μm was formed for thediameter bond by thermo-compression with a vacuum press etc., and madethem unify, not using a core substrate as wiring substrate 10. However,each insulating substrates 43 a-43 d include the layer in which theglass cloth was impregnated with insulating resin, respectively, and wassolidified platy. Other structure is the same as that of Embodiment 1.

Hereby, rigidity can be made high as the wiring substrate 10 whole.Therefore, even when the stiffener is omitted for cost reduction, a warpand a distortion of wiring substrate 10 can be prevented.

Embodiment 3

In Embodiment 3, heat radiation property is improved using the thingsmaller than Embodiment 1 as a filler mixed in heat radiation resin 31.Concretely, the filler whose average particle diameter is 5.8 μm andwhose maximum grain size is 24 μm is used.

And in order to control the thickness of heat radiation resin 31, aspacer which includes globular form zirconia is mixed in heat radiationresin 31. Concretely, the spacer whose average particle diameter is 25μm and whose maximum grain size is 33 μm is used. The thickness of heatradiation resin 31 is controllable by this spacer to 60±20 μm.

That is, the desired thickness of heat radiation resin is set to A,average particle diameter of a spacer is set to C, and a spacer ischosen so that it may have the relation:A× 9/10≦C.Hereby, the thickness of heat radiation resin is controllable withinfixed limits centered on desired thickness.

And by setting the maximum grain size of a filler to B_(MAX), and themaximum grain size of a spacer to C_(MAX), a spacer is chosen so that itmay have the relation:C_(MAX)>B_(MAX).Hereby, the thickness of heat radiation resin is controllable by not afiller but a spacer.

Average particle diameter of a filler is set to B, the minimum particlesize of a spacer is set to C_(MIN), the particle diameter which occupies90% of the occupying rate of a filler is made into B_(90%), and a spaceris chosen so that it may have any of relations:C>B_(MAX).C_(MIN)>B,C_(MIN)>B_(90%).Hereby, the utilization efficiency of a spacer can be improved.

In order to improve heat radiation property, the content in heatradiation resin of a spacer is made to less than or equal to 10 volume%, and preferably to less than or equal to 5 volume %.

Embodiment 4

In Embodiment 4, the flow property of heat radiation resin 31 whichadheres semiconductor chip 22 and heat spreader 32 is set as thefollowing values. Here, the flow property of heat radiation resin 31shall be decided by making 1 g heat radiation resin dropped on a planefrom the 10 mm upper part at room-temperature 25° C., and measuring thebreadth of the heat radiation resin.

Conventionally, in this measuring method, the heat radiation resin ofthe flow property whose breadth is 19 mm was used. However, since resinis still a liquid state which has not solidified in the transportationafter mounting heat spreader 32 on semiconductor chip 22 after mountinguntil curing when a stiffener is omitted, there was a problem that adrift of heat spreader 32 occurred by an oscillation and an inclination.

On the other hand, in Embodiment 4, the heat radiation resin of the flowproperty whose breadth is 4 mm or more, and 12 mm or less, for example,8 mm, is used in the above-mentioned measuring method. Thus, a drift ofheat spreader 32 can be prevented by using the heat radiation resin offlow property whose breadth is 12 mm or less. Since it fully gets wetand spreads when heat radiation resin 31 is applied on semiconductorchip 22 by using the heat radiation resin of flow property whose breadthis 4 mm or more, the generation of void can be prevented.

1. A semiconductor device, comprising: a wiring substrate; asemiconductor chip flip-chip-bonded over the wiring substrate; and aheat spreader adhered over a back surface of the semiconductor chip withheat radiation resin; wherein the heat radiation resin contains a fillerand a spacer; by setting a thickness of the heat radiation resin to A,and an average particle diameter of the spacer to C, a relation of A×9/10 ≧C is held; and the average particle diameter of the spacer islarger than a maximum grain size of the filler.
 2. A semiconductordevice according to claim 1, wherein a maximum grain size of the spaceris larger than a maximum grain size of the filler.
 3. A semiconductordevice according to claim 1, wherein a minimum particle size of thespacer is larger than an average particle diameter of the filler.
 4. Asemiconductor device according to claim 1, wherein a minimum particlesize of the spacer is larger than a particle diameter which occupies 90%of an occupying rate of the filler.
 5. A semiconductor device accordingto claim 1, wherein a content in the heat radiation resin of the spaceris less than 10 volume %.
 6. The semiconductor device according to claim1, wherein the spacer includes globular form zirconia.